Electromagnetic contact device



J. C. DAVIS ELECTROMAGNETIC CONTACT DEVICE Dec. 24, 1963 Filed March 31, 1959 2 Sheets-Sheet 1 INVENTOR. fl /W a 2% United States Patent This invention relates to electrical switch and more particularly comprises a new and improved positive acting contact evice.

Snap acting switching devices now available have certain features which disqualify their use in many applications. For example, the force required to overcome a spring or raise a weight which provides the snap action of the switch is not always available. in some cases, this diiliculty may be overcome by relaxing the spring or reducing the weight but unfortunately, this is often accompanied by arcing and high resistance at the contact points. In such devices as timers and counters, it is absolutely essential that the cont-act points open and close cleanly and that false repetition be avoided.

Generally problems arise either when the switch actuator moves slowly or when the actuator may stop at any unforseen location. In this case, the contacts often are or remain closed beyond the intended period.

The primary object of my invention is to provide an actuating action for contacts which under positive action causes the contacts to open immediately after being closed by the actuator, even though the actuating motion may have been imperceptibly slow or hesitant.

Another important object of my invention is to prevent a single action of a switch actuator from closing the switcn contacts more than once.

Another object of my invention is to provide a contact device which may be firmly closed with the slightest application of force.

Another object of my invention is to provide a contact device which automatically closes tichtly immediately upon the initial touching of the contacts.

Still another important object of my invention is to provide a contact device which automatically closes and opens once only in response to a single actuation.

Yet another object of my invention is to provide a contact device which cannot are or repeatedly close in response to a single actuation.

To accomplish these and other objects, several embodiments of my invention include among their important features a pair or contact points at least one of which is carried on a movable blade. An actuator operated by some external member is positioned to move the blade to close the contacts. The initial light closure of the contacts under the feeble torque of the actuator energizes a coil the ilux of which is devoted solely to pressing the contacts more tightly together. Thus, the contact resistance decreases and the current fiow increases in the circuit as a continuous and irreversible process. This insures a firm and positive closure of the contacts and avoids chattering and hesitating. in the same circuit another coil is energized and its flux acts to cause relative movement between the contacts as a sub-assembly, and the actuator. The relative movement may be described as a step-over movement in that it frees the actuator from its engagement with the contact blades so that their spring tension may open them which deenergizes the circuit and restores it to a normal condition. Due to the step-over" feature of the mechanism, no further contact action can take place until further activity by the actuator. Another signal in the form of repeated or continued mechanical motion must arise from the actuator to effect any further contact operation. In other embodiments of my invention, the first coil is eliminated. Thus, the closing of the contacts by the actuator imme- 2. lately causes energization and operation of the coil to eilect a relative movement between the contacts and the actuator and the release of the contacts.

These and other objects and features of my invention will be better understood and appreciated from the following detailed description of several embodiments thereor", read in connection with the accompanying drawings, wherein:

FIGURES l, 2, 3, 4 and 5 are elevation views of live different embodiments of my invention;

FIGURE 6 is a side elevation view of the embodiment shown in FlGURE 5;

FIGURE 7 is an elevation view of still another embodiment of my invention; and

FlGURES 8 and 9 are diagrammatic views of a portion of the apparatus shown in FYURE 7 and suggest the alternative positions of the assembly.

T he embodiment of my invention illustrated in FIG- URE 1 includes a pair of contacts it and 12 carried on blades 1 and 16 respectively. The contacts lid and 12 are normally open as hown in the drawing and are controlled by an actuator A pivotally mounted at on an armature 22, gravity biased against its stop. Gbviously, wherever the requirements of a particular application preclude the use of gravity as a reliable bias in any of the embodiments of my invention the designs can equally embody a spring bias. When the actuator is turned clockwise as shown in 1 it engages the lower portion of the blade id and moves the contact til into engagement with the contact A sprocket 24 illustrated diagrammatically and rotatable in the direction of the arrow as is disposed adjacent to the lower end of the lever 13 and when rotated as suggested pivots the actuator about pivotal mounting causing it to close the contacts if; and 7.2 in the manner described. A coil 23 is disposed adjacent the end 3% of the armature and when energized, pivots the armature about its pivotal support 32 in a clockwise direction from the normal position illustrated. The same action carries the actuator upwardly above the end of the blade of sprocket. The coil is energized through an elect -ical circuit which includes the leads 3d and The contacts and i2 interrupt the lead 34, and, therefore, the coil may be energized only by the closing or" the contacts.

In operation, as each blade of the sprocket engages the lower end of the actuator it the actuator closes the contacts and 12. Closed contacts Ill) and 12 complete the circuit to the coil 2% causing it to become energized. The energized coil attracts the armature which carries the lower end of the actuator over the particular sprocket blade which ellected the actuation. Thus, the actuator steps-over the end of the sprocket blade, is released, and free to pivot on its support Ell between the limits of the stops 38 and The snap action of the blade lid breaks the contacts cleanly and no arcing may occur.

It should be appreciated that each blade of the sprocket 2 can actuate the contacts just once because of the stepover action of the actuator. Moreover, r ardless of the position in which the sprocket stops, the c a not remain closed, for once closed, the actuator a ly promptly causes them to open.

The embodiment of FlGURE 2 is very similar to that shown in FIGURE 1 and its operation will become apparent from the following rief description. A pair of blades and each carries one of the contacts and 4-5 and the blades bias the contacts to an open position. A sprocket having a plurality of actuating blades turns in the direction of the arrow 52. and each blade it} is adapted to move the blade to the left as illustrated gear (not shown) mounted concentrically with the pivotal support 56. As a result, the motion of the arms.- ture 5-?- as it pivots on iLS support will not destroy the mesh of the sprocket and drive gear.

The armature is biased to the position illustrated by a spring and a coil 69 when energized moves the armature against the bias of the in a counter clockwise direction causing the end 62 of the armature to enthe pole e 6 5. The coil is energized through a circ vhich includes the contacts and as. in operation, as the sp turns, its actuating blades cnthe stem of the blade 42 moving it to the left and the contacts r"-. The closed con: F and complete the circuit to the coil so. 1

(ts the arm ture 5d and cans t to move downwardly with it so that the bl id 43 and particularly tne stem 6a is freed of the actuating i de St? and steps-over it. The step-over action is by the slight rotation of the sprocket 43 as it moves in an arc with the armature. Obviously, the embodiment of F URE 2 has all the advantages of the previously described embodiment and therefore they need not be relin each of the embodiments of FlGURES 1 and 2 the closing of the contacts immediately sets into action the assembly which cause them to open. In the embodiments of FEGURES 36, an intermediate step is introduced into the action of the switch which presses the contacts more tightly together. This phenomenon will be described below in connection with those figures.

embodiment of my invention shown in FEGURE 3, like that in FlGURE 1, includes a pair of contacts and y open contacts are controlled by an actuator 76 pivy .rounted at 1 3 on an armature gravity biased st its stop. When the actuator pivots clockwise as shown, it engages the lower end of the blade 72, and moves it to the right to close the contacts.

A sprocket rotatable in the direction of the arrow has a number of blades each of wh'ch is adapted to engage the lower end of the actuator 7s and cause it to pivot clockwise in the manner described above and close the contacts 6 3 and 7t.

A pair of coils and are wound on a common core and each is ele rically energized through a circuit which includes the contacts 68 and 79. The coil 88 controls a pivotally mounted armature 92 supported on a pin 93 and when energized draws the arm 9'6 of the ar nature to its pole piece vi hen the armature 2 is pivoted in this ma lllf under the influence of the coil its other arm engages the angle or ii" rge T32 of the actuator '15 car. ing a firmer engagement between the conta ts and 7d. Thus, the armature serves as a Moreover,

by n

:lv closi the contacts and the resistance at the point of c ct is reduced, which a lows a greater current to how through the circuit. Thus, the coil and associated com onents are devoted solely to pressing the contacts toge r 4.1 response to the light closure of the contacts under the fee le torque of the actuator.

The second coil as controls the armature 3% which is pivotally supported on a pin =34. The armature 8Q normally is positioned as shown in the drawing but is drawn upwardly about its pivot in response to energizstion of the coil a When the a. mature is moved u, dly in this manner, the flanged end N2 of the actuator 76 rides upwardly above the 1% on the end of the arm loll of armature if the sprocket no longer gages the lower end of the actuator "7-5, th-

actuator will ivot point 78 and r lease the b e lying the contact released, the olade 72 moves to the left until it is engagcd by the stop will be noted that the circuit lid is connected to a power source through the contacts and 7 and that circuit includes two parallel branches for energizing tn curate coils and in operation, the contact dece shown in rlGURE 3 operates as follows:

Assume that the sprocket $2 is dri n by the rotation of a timer, counter, or some other sinnlar device. With the sprocket in the position illustrated, the armat res and are released and contacts and are open. As the sprocket @2, turns counter clockwise as suggested by the arrow, the blade engages the lower end of the actuator F6 causing it to pivot in a clockwise direction about the pin The pivotal action of the actuator in this direction moved the blade F2 carrying the contact ltt. The light closure of the contacts closes the and ene izes the coils. The coil is such very small curren flow required to attract Thus, the it al llow of current causes th armature to move in a counter clockwise direction about its pivot 94. The counter clockwise movement of the armature 92 causes the to engage the flange of the actuator id and the actuator applies a greater e against the blade to make a better closure of the contacts. Thus, chattering and hesitatin" of the contacts is eliminated and current flow increa es. increased current flow causes the one 'zed coil to attract the armature 8'2, and p-.=.rticularly its mange Elli to the pole piece 114. The pivotal action of the armature about its support ltld raises the fulcrum 73 of the actuator 76 so that the lower end of the actuator lies above the upper end of the blade 85 of the sprocket Moved upwardly in this manner, the actuator '76 steps-over the sprocket and its upper end is released from the control of the arm of the armature @2. The ilexible nature of the blade '72 urges the contact 63 to the left, out of engagement with the contact point 76*. Little if any resistance to the action is encountered by the blade for the actuator '76 freely pivots on its support '23, blade of the sprocket -32 having passed beneath its lower end.

From the foregoing description, it will be apparent that each time a blade of the sprocket 82 engages tl e lower arm of the actuator, a tight closure and, thereafter, an opening of the contacts occurs. There can be no arcing between the contact points because of the substantially instantaneous release of the actuator 76. chattering and hesitating or" the switch action is eliminated because of the manner in which the armature 92 firmly closes the contacts during the first stage in the operation. Furthermore, false repetition of the action is totally eliminated.

In the embodiment of my invention shown in FIGURE 4, a similar arrangement is employed to cause the positive closing and opening of the contacts. in this embodiment, the contacts 123 and 122 are carried by flexible blades 124 and 125, respectively. The blade 126 extends downwardly below the contact 122 and lies in the path of the blades of the sprocket 121*. The sprocket 125 is carried by a pivotally supported armature biased to the position illustrated by the spring 132. The described structure is identical to that shown in FIGURE 2.

A second armature 13d pivotally supported on pin 13-5 has a flange 13'? formed at one end which engages the blade of the switch. The armature Ht) pivotally supported on the pin ltdtl is controlled by a coil 142 energized through a circuit dominated by the contacts 129 and 122. The armature f d is controlled by a second coil which is also energized through the circuit controlled by the contacts 129 and 12-2.

Assume that the sprocket 12 8 continuously rotates in a counter clockwise direction as suggested by the arrow. As each blade of the sprocket engages the lower end of the blade 126, the contact 1122 moves into engagement with the contact 1% and current flows to the coils 142 and 144. Coil 14 i is so wound so as to be more responsive to the initial flow of current and causes the armature 13d to pivot about its mounting 136 in a counter clockwise direction. Moved in that direction, the flange 1258 of the armature 34 pushes the blade 12% carrying the contact lZtl to the right so that the contacts are held iirnily together. The firmer closing of the contacts causes more current to flow and coil i 52 attracts the armature 134 against the bias of the spring 132? As the armature 13% moves downwardly to the pole piece of the coil M2, the blade 126 steps over the blade of the sprocket i218 and is released. The release of the blade 1.25 causes the contact 122 to move out of engagement with the contact liZil and the circuit is opened. The opening of the electrical circuits controlling the coils M2 and 14 i cause each to release its armature so that the device returns to the position illustrated. Again, it will be appreciated that no false repetition of the closing of contacts 12% and H2 may occur, and arcing and chattering are eliminated. As explained in connection with the embodiment of lGUltli 2, the sprocket 128 normally would be driven either directly or indirectly by a gear (not shown) mounted coaxiaily with the pivot or the armature As a result, the drive of the sprocket will not be disturbed by the movement of that armature. Furthermore, the arcuate movement of the sprocket 128 on the armature 13% will aid the blade 126 as it steps over the sprocket blades.

in FlGURES and 6 another embodiment of my invention is illustrated. in this embodiment, a vertical plate carries a pair of spaced :1 art contact fingers and 154 on an insulation block 156. The plate 150 is supported by two pairs or parallel arms 1555, led and 162, Each of the arms is pivotal-ly secured at one end to an edge of the plate llitl and at its other end to the support res. The pins 168 which pivotally connect the ends of the arms res and lo l to the support res slide freely in slots 170 formed in the support. Thus, the pins 168 not only serve to support those arms for pivotal movement, but in addition, permit translational movement or" the arms on the support Fingers 152 and 15d carry at their lower ends contacts 172 and 17 which are adapted to be closed by the metal strips 175 carried on the outer end of each of the blades 178 of the sprocket 18b.

Disposed behind the plate 1% is a coil secured by a frame 1% to the support 165. The coil 182 is controlled by a circuit dominated by the contacts 172 and 17d.

The embodiment of the contact device shown in H6- URES 5 and 6 operates as follows:

Assume that the sprocket is rotating counter clockwise as shown. As the metallic sh. 17% engages the contacts 172 and i174, the coil is energized and the plate 155i is attracted to it. The weight of the movable part of the parallelogram assembly which includes the plate lt-Zta as well as the contact fingers supported from it along with the arms i555, laid, it and preclude it from moving upward under the initial flux resulting from the light closure of the contacts. Rather, the arms is and 164 will move to the ri ht in their slots lid and no lower portion of the plate will move toward the pole piece of the coil, and the plate will be at an angle to the vertical. This action of the plate 15% causes a firmer engagement of the strip lill with the contacts 172, and 174 and an increased current flows throu h the coil The increased current through the coil 82 will then cause the parallelogram assembly to move upwardly if a gap exists between the pole piece and the plate The upward movement of the plate carries the contact fingers 152 and 154 with it and they step over the end of the blade of the sprocket bus, the circuit through the contacts 172 and i7 5 is broken and the col 182 is deenergized. As a result, the parallelogram assembly returns to the position shown with the contacts in the path of the next blade of the sprocket.

Those familiar with the art will appreciate that the embodiment of my invention shown in FlGURES 5 and 6 has the same advantage as the other embodiments of my invention. No arcing may occur between the contests and once actuated the contacts close firmly and then open without any further control being exerted upon them. Further action on the part of the actuator is required to close the contacts again.

in each of the embodiments of my invention described above, the characteristic motion of the actuator is continuous and unidirectional. It should be understood that the invention, however, finds application in many other forms. Thus, the step-over principle may be applied to reciprocating motion which is either of a steady and predictable character or alternatively haphazard and unpredictable. ln Ft'GURES 7-9, I have illustrated such an arrangement. Here, the actuator is controlled by and moves with an indicating pointer of an indicating instrument such as a volt meter, ammete temperature gage, pressure gage, position indicating servo, etc.

Referring to PEGURE 7, the reader will note that a pair of contacts 1% and are carried on blades 1% and 2%, rec, -ctively. The contacts lie in the path of travel of an actuator carried on the pointer of an indictating instrument generally designated at 23 2. As suggested by the broken line he entire contact assembly is mounted concentric with the pointer shaft. The frame of the assembly is srrported at on the shaft and thus, as the pointer swings left or right from the n utral position shown, the actuator 39% engages one of the two contacts and 3%.

The blades 1% and 1% are carried on a paralleloram support which includes an armature Eli) and a strut tpivotally mounted on the frame 2% by pins and 6, respectively. Arms E18 and 221;"; are pivotally conn cted to the ends of the armature 2M) and strut Zl-"i and carry the blades and on insulation blocks and 224 as illustrated.

The parallelogram support is controlled by a pair of coils 225i and carried by the frame 2%. The coils which as described below are alternately energized by the contacts 1% and 192 attract the armature 21b and rock the parallelogram assembly between the positions suggested diagrammatically in FlGUiZES 8 and 9. Thus, when th coil becomes energized, the armature 21-6 pivots on the pin 21?. and moves the assembly to the position shown in PZG'URE 8. Encrgization of the coil 23% acts in a direction opposite to that of the coil 2-23 in that it pivots the armature 23rd in a counter clockwise direction causing the assembly to assume position shown in FlGU E 9.

The reader v note in FlGURES 8 and 9 that when the assembly pivots in response to energization of one or the coils, the contacts and move in a generally radial direction w respect to the 2% in opposite directions. Thus, when the coil 228 is energized, the cont act I199 rises while contact HZ drops closer to the axis 2%. Energiz-ation of the coil 22s produces the opposite erlect.

The asse bly shown in FIGURE 7 is suitable for use as a limiting device in combination with the indicator. The operation of the combination will be described as used for such a purpose. it will be noted in FIGURE 7 that I have suggested means at and which enable operator to vary the distance between the contacts 3% and Each arm 2'18 and is a split and is secured together by pins which may be assembled selectively in the various holes 266 provided. By varying the effective length of the arms, the distance be tween each contact and the center posi on of the pointer may be changed to alter the high and low limits.

As the assembly will not normally assume the position shown in FlGURE '7, but rather will be oriented be men 7 either as shown in FIGURES 8 or 9, assume that the assembly is rather in the position shown in 8 with the contact 19% in the raised pos The spring which extends between the pin on the 2 i which forms part of the strut and the pin 256 on the frame 2th? acts as a toggle and snaps the a bly into the positions shown in FEGURES 8 and 9. i e particular position is determined by the position or the axis of the spring with respect to the center line defined by the pins 212 and As the spring passes over enter from one side of the line to the other, it snaps the assembly to the side approached. When the pointer pivots counter clockwise on its shaft and the assembly is hold by the spring 25s in the position of FIGURE 8, the contact 19" will be engaged by the actuator 193 the coil actuator J leads 23d and 232, the lead contact 1198,

" ation of 19S and pointer 23%, and the lead the coil 2 26 will immediately cause the par rograrn assembly to snap to the posit on shown in FlGURE When this occurs, the contact moved away from the actuator 93 and the circuit to the coil is broken. This action, it will be recogn zed, is sstep-over action employed in the other embodiments of my invention. That is, as coil 2226 is energized, the contact 393 is moved to the lower position out of engagement with the actuator 19%. in the lower position, the contact cannot again be engaged by the actuator to complete the circuit to the coil 22.6 until the other coil 22-3 has intervened. bec energized to That is, until the coil and return the parallelogram assembly to the position shown in FIGURE 8, the actuator I198 cannot engage the contact 1%.

Now assume that the pointer 21% moves in a clockwise direction in response to an increase the condition sensed by the indicator. When the pointer Elli) moves far enough so that the actuator 1 engages the contact 192, the coil 228 becomes energized through the circuit which includes the leads 23d and 238, the lead the contact 292,, the actuator and the pointer 28d, the lead 2 3 s. Energization of the coil as stated above, causes the parallelogram assembly to snap to the position shown in FIGURE 8, and the contact 192 moves down wardly out of engagement with the actuator 1198. Thus, in effect, the closing of the contact 192 immediately causes the circuit which is controlled by that contact to become tie-energized. Here again, a signal could not be impressed upon the coil 223 until the other coil is energized to intervene, for only then wil the contact 192 again assume a position wherein it can be engaged by the actuator. Thus, the instrument shown in 1U URE 7 includes two step-over arrangements and one and only one signal can be produced each time the pointer fail-d moves to an extreme position.

Because of the manner in whthe parallelogram assembly moves, no chattering or a. can occur between the actuator 39:? and either of the con tacts.

In each embodiment of my invention, an output signal may be obtained as a result of each operation of contact device by an electrical indicator or rel-y con nected in series with the power source, i.e. in ser as with the coil causing the step-over action. in certain enibodiments for certain applications might be feasible to position an auxiliary pair of contacts to be operated by the coil and armature used for the stepover movemerit' The auxi"ary contacts could be connected into another electrical circuit and initiate the outpi signal. This, in effect, would combine the step-over coil with a relay and would result in a compact design desir bio for ertain applications.

Gbviously, numerous modifications may be made of my invention without departing from its spi Therefore, i do not intend to limit the breadth of my invention to the specific embodiment illustrated and described. Rather, it is my intention that the b dth of my invention be determined by the following claims and their equivalents.

I claim:

1. A contact device comprising a pair of normally open contacts, a blade carrying one of the contacts, a coil, an energy source, a circuit including the contacts connected to the source and the coil and energizing the coil when he contacts close, a movable armature controlled by the coil, and an actuator carried by and movable with the armature and positioned to engage the blade and close the contacts only when the coil is deenergized, whereby the closing of the contacts moves the armature and causes the actuator to release the blade.

2. A device as defined in claim 1 further characterized by the movement of the armature causing the blade to step over the actuator.

3. A contact device comprising a pair of open contacts, a coil energized by the closing of the contacts, a pivotally supported armature pivoted to a first position by energizertion of the coil, means biasing the armature to a second position away from the coil when the coil is deenergized, and a sprocket carried by the armature and positioned to close the contacts upon its rotation when the armature is in the second position away from the coil, said sprocket passing beneath the contacts when the armature moves to its first position in response to energization of the coil.

4-. A contact device comprising a pair of contacts movable to opened and closed positions, actuating means normally disposed adjacent the ends of and to one side of the contacts for moving the contacts to one of said positions, a coil operatively connected to the contacts and energized by the moving of the contacts to said one position, and an armature movable in response to energizetion of the coil and carrying one of the actuating means and contacts and positioning the actuating means relative to the contacts beyond the end of and to the other side of the contacts upon energization of the coil so that the contacts step over the actuating means and move to the other position, said armature being biased to a position wherein the actuating means is disposed in its normal position.

References (fitted in the file of this patent UNlTED STATES PATENTS 

1. A CONTACT DEVICE COMPRISING A PAIR OF NORMALLY OPEN CONTACTS, A BLADE CARRYING ONE OF THE CONTACTS, A COIL, AN ENERGY SOURCE, A CIRCUIT INCLUDING THE CONTACTS CONNECTED TO THE SOURCE AND THE COIL AND ENERGIZING THE COIL WHEN THE CONTACTS CLOSE, A MOVABLE ARMATURE CONTROLLED BY THE COIL, AND AN ACTUATOR CARRIED BY AND MOVABLE WITH THE 